U.S. patent number 11,402,030 [Application Number 16/871,120] was granted by the patent office on 2022-08-02 for adjustment of stroke end positions of a process control valve.
This patent grant is currently assigned to Burkert Werke GmbH & Co. KG. The grantee listed for this patent is Burkert Werke GmbH & Co. KG. Invention is credited to Klaus Beck.
United States Patent |
11,402,030 |
Beck |
August 2, 2022 |
Adjustment of stroke end positions of a process control valve
Abstract
A method of adjusting stroke end positions of a process control
valve is provided. A valve control mechanism is set up to
continuously determine an actual position value from a
travel-measurement system value acquired by a travel-measurement
system, taking a first travel-measurement system final value and a
second travel-measurement system final value into account. The
method comprises the recognition of a first stroke end position
when the process control valve is fully closed, and the recognition
of a second stroke end position when the process control valve is
fully open. The method further comprises the storage of the
travel-measurement system value corresponding to the first stroke
end position as the first travel-measurement system final value,
and the storage of the travel-measurement system value
corresponding to the second stroke end position as the second
travel-measurement system final value. The process control valve is
a component of a process plant, and the steps of an associated
process are carried out during operation of the process plant. The
disclosure further relates to a corresponding program code, to a
valve control mechanism, and to a process control valve.
Inventors: |
Beck; Klaus (Ingelfingen,
DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Burkert Werke GmbH & Co. KG |
Ingelfingen |
N/A |
DE |
|
|
Assignee: |
Burkert Werke GmbH & Co. KG
(N/A)
|
Family
ID: |
1000006467174 |
Appl.
No.: |
16/871,120 |
Filed: |
May 11, 2020 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20200362978 A1 |
Nov 19, 2020 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16K
37/0025 (20130101); G05B 19/4183 (20130101); G05B
19/41845 (20130101); F16K 31/02 (20130101) |
Current International
Class: |
F16K
31/02 (20060101); G05B 19/418 (20060101); F16K
37/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Keasel; Eric
Attorney, Agent or Firm: Carlson, Gaskey & Olds,
P.C.
Claims
The invention claimed is:
1. A method of adjusting stroke end positions of a process control
valve; wherein the process control valve comprises a process valve
having an actuator and a valve housing, and wherein the process
control valve comprises a valve control mechanism associated with
the process valve, and wherein the process control valve comprises
a travel-measurement system configured to acquire a
travel-measurement system value, wherein the valve control
mechanism comprises a storage unit which provides a first
travel-measurement system final value and a second
travel-measurement system final value and wherein the valve control
mechanism is configured and set up so as to continuously determine
an actual position value from the travel-measurement system value
acquired by the travel-measurement system, taking the first
travel-measurement system final value and the second
travel-measurement system final value into account; and wherein the
method comprises the following steps: a. recognizing a first stroke
end position when the process control valve is fully closed, b.
storing the travel-measurement system value corresponding to the
first stroke end position as the first travel-measurement system
final value, c. recognizing a second stroke end position when the
process control valve is fully open; and d. storing the
travel-measurement system value corresponding to the second stroke
end position as the second travel-measurement system final value;
wherein the process control valve is a component of a process plant
and the steps of the method are carried out during operation of the
process plant.
2. The method according to claim 1, wherein the first stroke end
position is recognized when an acquired travel-measurement system
value is smaller than the provided first travel-measurement system
final value.
3. The method according to claim 1, wherein the second stroke end
position is recognized when an acquired travel-measurement system
value is greater than the provided second travel-measurement system
final value.
4. The method according to claim 1, the method comprising the
following step: modifying a position set-point value by which the
process control valve is driven, wherein a modified position
set-point value is reduced by a defined value compared to the
position set-point value, provided that the position set-point
value drives the process control valve so as to close completely,
and/or wherein the modified position set-point value is increased
by a defined value compared to the position set-point value,
provided that the position set-point value drives the process
control valve so as to open completely.
5. The method according to claim 4, wherein the method is
terminated if upon driving using the modified reduced position
set-point value, a resulting travel-measurement system value does
not fall below the provided first travel-measurement system final
value, and if upon driving using the modified increased position
set-point value, the resulting travel-measurement system value does
not exceed the provided second travel-measurement system final
value.
6. The method according to claim 1, wherein the first and/or the
second stroke end position is acquired if a discontinuous
transition to a stationary value in a derivative function of the
actual position value is recognized.
7. The method according to claim 1, wherein the first stroke end
position is recognized when an acquired travel-measurement system
value is smaller than the provided first travel-measurement system
final value when the process control valve is driven by a position
set-point value so as to close completely, and when the acquired
travel-measurement system value is stationary.
8. The method according to claim 1, wherein the second stroke end
position is recognized when an acquired travel-measurement system
value is greater than the provided second travel-measurement system
final value when the process control valve is driven by a position
set-point value so as to open completely, and when the acquired
travel-measurement system value is stationary.
9. The method according to claim 1, wherein the first and/or the
second stroke end position is acquired if a discontinuous
transition to a stationary value in a derivative function of the
actual position value is recognized, and wherein recognition of the
discontinuous transition is carried out using a differentiating
filter.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a U.S. non-provisional application claiming the
benefit of German Patent Application No. 10 2019 112 725.4, filed
on May 15, 2019, which is incorporated herein by its entirety.
TECHNICAL FIELD
The disclosure relates to a method of adjusting stroke end
positions of a process control valve. The disclosure further
relates to a corresponding program code for execution on a valve
control mechanism, to a valve control mechanism, and to a process
control valve.
BACKGROUND
In the manufacture of process valves, individual components such as
the valve housing and the drive are each subject to various
tolerances. This applies in particular to the stroke end positions,
which result from the connection of the drive to the valve housing
and which slightly differ individually.
The adjustment of the stroke end positions of a process control
valve at the factory or when commissioning a plant is often carried
out by an automatic "tune function". To this end, microcontroller
electronics in the control head/positioner is used to move the
valve to the end positions. The fitting is then fully opened and
fully closed. This is not possible during operation of a plant.
The same applies to the subsequent replacement of a process valve
drive and/or a control head/positioner in a plant. Here, the stroke
end positions must also be adjusted regularly.
However, since the adjustment of the stroke end positions cannot be
carried out during the ongoing process operation, the replacement
of a process valve in a plant regularly leads to additional
downtime, which considerably exceed the actual assembly time.
The intervention in the regular operation of the plant is to be
minimized as far as possible and the fluidic function of the plant
is to be impaired as little as possible during the first
installation or a later (re-) adjustment or the later replacement
of a process valve.
SUMMARY
According to one exemplary disclosure, adjustment of the stroke end
positions is carried out during operation of the plant. The
operation of the plant does not have to be interrupted for the
adjustment. An appropriate method of adjusting stroke end positions
of a process control valve is provided.
A process control valve regularly includes a process valve having
an actuator and a valve housing, and a valve control mechanism
assigned to the process valve and a travel-measurement system.
According to one aspect, the valve control mechanism provides a
first travel-measurement system final value and a second
travel-measurement system final value in a storage unit. Predefined
default values for the stroke end positions may be pre-allocated to
the first travel-measurement system final value and the second
travel-measurement system final value. The valve control mechanism
is configured and set-up so as to continuously determine an actual
position value from a travel-measurement system value acquired by
the travel-measurement system, taking the first travel-measurement
system final value and the second travel-measurement system final
value into account.
According to a further aspect, the method comprises the recognition
of a first stroke end position when the process control valve is
fully closed, and the storage of the travel-measurement system
value corresponding to the first stroke end position as the first
travel-measurement system final value.
The method further comprises the recognition of a second stroke end
position when the process control valve is fully open, and the
storage of the travel-measurement system value corresponding to the
second stroke end position as the second travel-measurement system
final value.
The process control valve is part of a process plant, and the steps
of the method are carried out during operation of the plant.
In other words, the valve is not proactively opened and closed for
adjustment, which is usually in conflict with the normal processes
and would disturb the ongoing operation of the plant. The valve
control mechanism rather changes to a kind of monitoring mode for
the adjustment, in which it waits until the valve is fully open or
closed anyway due to the process.
According to an advantageous aspect, the first stroke end position
may be recognized if the acquired travel-measurement system value
is smaller than the provided first travel-measurement system final
value.
In order not to overwrite the travel-measurement system final value
unnecessarily often, it may be provided as an additional condition
for the recognition of the final stroke position to wait until the
process control valve is driven by a position set-point value so as
to close completely. Preferably, the acquired travel-measurement
system value is stationary.
Similarly, the second stroke end position may also be recognized if
the acquired travel-measurement system value is greater than the
provided second travel-measurement system final value.
Advantageously, an additional condition may be that the process
control valve is driven by a position set-point value so as to open
completely. Preferably, an additional condition may be that the
acquired travel-measurement system value is stationary.
According to a further advantageous aspect, the method may comprise
the modification of a position set-point value by which the process
control valve is driven. The modified position set-point value can
be decreased by a defined value compared to the position set-point
value when the position set-point value drives the process control
valve so as to close completely. Similarly, the modified position
set-point value can be increased by a defined value compared to the
position set-point value provided that the position set-point value
drives the process control valve so as to open completely. In other
words, this advantageous aspect provides that in the adjustment
mode, when the valve is fully opened or closed due to the process,
the valve is driven such that the drive is controlled beyond the
stored stroke end positions and moves up to the mechanical limit.
The defined value may be selected so as to cover the tolerance
interval resulting from the tolerance chain. In this way, the
mechanically induced stroke end positions may be reliably
recognized.
According to an advantageous aspect, the method can be terminated
if upon driving using a modified reduced position set-point value,
the resulting travel-measurement system value does not fall below
the provided travel-measurement system final value, and if upon
driving using a modified increased position set-point value, the
resulting travel-measurement system value does no longer exceed the
provided travel-measurement system final value. In this way, the
adjustment mode is automatically exited when the mechanically
induced stroke end positions have been recognized and
registered.
According to a further advantageous aspect, the first and/or the
second stroke end position can be recognized by the fact that in a
derivation function of the actual position value, there is a
discontinuous transition to a stationary value. Advantageously, the
discontinuous transition may be recognized by a differentiating
filter. This improves or simplifies the recognition/detection of
the stroke end positions.
Furthermore, a program code is provided which comprises a plurality
of instructions which during execution of the program code by a
valve control mechanism cause the latter to perform the steps of
the method according to the disclosure. Due to the program code,
the method may also be integrated into existing valve control
mechanisms.
Furthermore, a valve control mechanism is provided which is
configured and set up so as to execute the method according to the
disclosure, in particular wherein the valve control mechanism
contains a microcontroller which executes the aforementioned
program code.
Furthermore, a process control valve is provided which is
configured and set up so as to execute the method according to the
disclosure.
According to an advantageous aspect, the process control valve may
comprise the aforementioned valve control mechanism.
BRIEF DESCRIPTION OF THE DRAWINGS
The features and aspects of the disclosure are explained in more
detail below on the basis of examples embodiments and with
reference to the figures, in which
FIG. 1 shows a simplified representation of a process control valve
having a control head,
FIG. 2 shows a simplified representation of a process control valve
having a positioner,
FIG. 3a shows an exemplary representation of a POS-time curve for a
process control valve,
FIG. 3b shows an exemplary representation of a CTRL-time curve for
the process control valve,
FIG. 4a shows an exemplary representation of a POS-time curve for a
process control valve,
FIG. 4b shows an exemplary representation of a CMD-time curve for
the process control valve,
FIG. 5a shows an exemplary representation of a POS-time curve for a
process control valve, and
FIG. 5b shows an exemplary representation of a time curve of a
differentiating filter for the POS-time curve,
FIG. 5c shows an exemplary representation of a POS-time curve for
the process control valve, and
FIG. 5d shows an exemplary representation of a time curve of a
differentiating filter for the process control valve.
DETAILED DESCRIPTION
FIG. 1 shows a simplified schematic representation of a process
control valve 10 in a process plant 1, which comprises the valve
control mechanism 20 and the process valve 30.
The process valve 30 comprises the actuator 40 and the valve
housing 50. The process valve 30 may in particular be configured as
a seat valve or as a diaphragm valve.
In particular, the actuator 40 may be actuated pneumatically, by an
electric motor or electromagnetically. This depends on the local
requirements, for example on the performance, explosion protection
or also on the existing supply, for example with compressed
air.
The valve housing 50 has a flow channel 60. The valve control
mechanism 20 comprises the positioning system 70, the storage unit
80, and the travel-measurement system 90. The travel-measurement
system 90 may also be part of the process valve 30. The
travel-measurement system 90 comprises the travel sensor 95.
The valve control mechanism 20 is configured by way of example as a
control head. A control head is used for an open/close operation.
This means that in the case of a valve control mechanism 20a, only
the control signals CTRL "open" (100%) or "close" (0%) are
transmitted by the positioning system 70 to the drive of the
process valve 30 or to the actuator 40.
In the production of process valves, individual components are
subject to various tolerances. Important are, for example, the
mechanically induced stroke end positions 200 or 210 for each
process valve, which result from the connection of the drive to the
valve housing.
The process valve 30 is fully closed at stroke end position 200 and
it is fully open at stroke end position 210.
The predefined stroke end positions 200a and 210a are determined
such that they are always within the stroke range 220 of the
respective process valve 30, even when taking the stated tolerances
into account. These (generic) predefined stroke end positions 200a,
210a thus constitute default values for the travel-measurement
system final values 100, 110, which permit a sufficient functioning
of the process control valve 10.
Later, the travel-measurement system 90 is adjusted individually
such that the travel-measurement system final values 100, 110 of
the travel-measurement system 90 correspond to the stroke end
positions 200, 210 of the process valve 30.
According to the disclosure, such an adjustment is possible at any
time. It is therefore no longer necessary to adjust a process
control valve 10 before commissioning. Even if a process control
valve 10 is replaced in a plant 1, for example due to wear, it is
no longer necessary to adjust it before commissioning.
For this purpose, the valve control mechanism 20 includes a
functionality for adjusting the stroke end positions 200, 210
during plant operation, which will be referred to as B-Tune 300
from now on. Preferably, B-Tune 300 is implemented as a software
module, which is responsible in particular for the adjustment and
the storage of the travel-measurement system final values 100, 110
in the storage unit 80.
The valve control mechanism 20 is configured and set up so as to
continuously determine an actual position value POS from a
travel-measurement system value acquired by the travel-measurement
system 90, taking the first travel-measurement system final value
100 and the second travel-measurement final system value 110 into
account.
The method according to the disclosure comprises the recognition of
a first stroke end position 200 when the process control valve 10
is fully closed, and the subsequent storage of the
travel-measurement system value corresponding to the first stroke
end position 200 as the first travel-measurement system final value
100.
The method further comprises the recognition of a second stroke end
position 210 when the process control valve 10 is fully open, and
the storage of the travel-measurement system value corresponding to
the second stroke end position 210 as the second travel-measurement
system final value 110.
The process control valve 10 is part of a process plant 1. The
steps of the process are performed during operation of the plant 1.
Therefore, the plant operation does not have to be interrupted for
adjustment.
The process control valve 10 is configured and set up so as to
execute the process. The process is advantageously represented in a
program code. The program code comprises instructions which upon
execution of the program code in a valve control mechanism 20 cause
the valve control mechanism to perform the method described above.
The valve control mechanism 20 is configured and set up
accordingly, e.g. it has a microcontroller. The microcontroller
executes the program code.
The described method is also used in the further example
embodiments.
FIG. 2 shows a simplified schematic representation of a process
control valve 10 having a positioning member 75, also referred to
as positioner. The structure and the function substantially
correspond to the structure and function shown in FIG. 1. Identical
components and components/features having comparable functions have
the same reference numerals. A repeated description is omitted.
A positioner is used for continuous or proportional operation. This
means that with a valve control mechanism 20b using the positioning
member 75, any control signals CTRL from 0% to 100% are sent by the
positioning system 70 to the drive of the process valve 30 or to
the actuator 40 as a control signal.
The positioner comprises in particular the functional groups
composed of the travel sensor 90, the positioning system 70, and
the valve control mechanism 20b. The travel sensor 90 measures the
current positions of the valve. The valve control mechanism 20b
continuously compares the current position (actual position value
POS) with a position set-point value CMD specified via an interface
(often a standard signal input) and feeds the result to the
positioner.
If there is a system deviation, the positioning system 70 causes an
appropriate correction of the actual position value POS.
In addition, a PID controller implemented in the valve control
mechanism 20b may be integrated, by which, in addition to the
actual position control, a process control (e.g. of level,
pressure, flow rate, temperature, etc.) may also be carried out as
cascade control. The process controller is integrated into a
control loop. The valve position set-point value CMD is calculated
from the process set-point value and the actual process value via
the control parameters (PID controller). The process set-point
value can be specified by an external signal.
FIG. 3a shows a simplified representation of a POS-time curve for
the process control valve 10 of FIG. 1. The associated simplified
representation of the CTRL-time curve is shown in FIG. 3b.
A control head is used as a valve control mechanism 20. The
predefined stroke end positions 200a and 210a are stored in the
storage unit 80 of the valve control mechanism 20a as default
values at the beginning.
During the execution of B-Tune 300 during regular operation of the
plant 1, the position set-point value CMD or the control signal
CTRL for "open" (100%) is specified at any time t1.
At time t2, the actuator reaches the mechanically induced stroke
end position 210. The travel-measurement system 90 detects the
actual position value POS as a travel-measurement system final
value 110. If the detection is successful, the actual position
value POS is stored as a stroke end position 210 in the storage
unit 80. In other words, the second stroke end position 210 is
recognized if the process control valve 10 is driven by a position
set-point value CMD so as to open completely, and if the acquired
travel-measurement system value is greater than the provided second
travel-measurement system final value 110. The stroke end position
210 is advantageously recognized if the acquired travel-measurement
system value is stationary.
In the same way, the stroke end position 200 is stored in the
storage unit 80. At time t2 or any later time t3, the position
set-point value CMD or the control signal CTRL is set for "close"
(0%). At time t4 or t5, the actuator reaches the mechanically
induced stroke end position 200. The travel-measurement system
detects the actual position value POS as a travel-measurement
system final value 100. If the detection is successful, the actual
position value POS is stored as a stroke end position 200 in the
storage unit 80. In other words, the first stroke end position 200
is recognized when the process control valve 10 is driven by a
position set-point value CMD so as to close completely and when the
acquired travel-measurement system value is smaller than the
provided first travel-measurement system final value 100. The
stroke end position 200 is advantageously recognized when the
acquired travel-measurement system value is stationary, i.e. does
not change any more.
It is not important whether the second stroke end position 210 or
the first stroke end position 200 is recognized first. As soon as
both stroke end positions 200, 210 have been stored, the process
control valve 10 is adjusted and B-Tune 300 is terminated.
FIG. 4a shows a simplified representation of an exemplary POS-time
curve for the process control valve 10 of FIG. 2. The corresponding
simplified representation of the CMD-time curve is shown in FIG.
4b.
A positioner is used as a valve control mechanism 20. The
predefined stroke end positions 200a and 210a are stored in the
storage unit 80 of the valve control mechanism 20b as default
values at the beginning.
During the execution of B-Tune 300 during regular operation of the
plant 1, whenever the positioning member 75 receives a position
set-point value CMD of 0% or 100%, a control signal CTRL is
specified from a modified position set-point value CMD* of (0-X) %
or (100+X) %. Here, the value X is greater than the largest
possible tolerance width. In other words, the following queries
take place in B-Tune: If "0%<CMD<100%", then CMD*=CMD; If
"CMD=100%", then CMD*=CMD+X; If "CMD=0%", then CMD*=CMD-X. As long
as the actual position value POS reaches values beyond 0% or 100%,
the actual position value POS is stored as the new
travel-measurement system final values 100 or 110 in the storage
unit 80. As soon as the actual position value POS no longer falls
below or exceeds 0% or 100% during this CMD* specification, the
process control valve 10 is "adjusted" and the B-tune "mode" with
the internal CMD* specification is terminated.
In other words, the procedure comprises the modification of a
position set-point value CMD by which the process control valve 10
is driven. The modified position set-point value CMD* is decreased
by a defined value X compared to the position set-point value CMD,
provided that the position set-point value CMD drives the process
control valve 10 so as to close it completely. The modified
position set-point value CMD* is increased by a defined value X
compared to the position set-point value CMD, provided that the
position set-point value CMD drives the process control valve 10 so
as to open it completely. In this way, the stored or predefined
stroke end positions 200a, 210a are passed over in a controlled
manner to determine the mechanically induced stroke end positions
200, 210.
The method is terminated if upon driving using a modified reduced
position set-point value (CMD*), the travel-measurement system
value resulting from the reduced position set-point value CMD* does
not fall below the provided travel-measurement system final value
100, and if upon driving using a modified increased position
set-point value CMD*, the provided travel-measurement system final
value 110 is not exceeded by the travel-measurement system value
resulting from the increased position set-point value CMD*.
FIGS. 4a, 4b show an exemplary B-tune procedure. At time t4, a
position set-point value CMD of 90% is specified. Since it is
neither a specification of 100% nor a specification of 0%, this CMD
is sent to the actuator 40 as a control signal CTRL.
At time t5, a position set-point value of 100% is specified. Since
it is a 100% specification, CMD*100+X is generated and sent as a
control signal CTRL to the actuator 40, which reaches the required
position at time t6. The actual position value POS measured by the
travel-measurement system 90 is now stored as a stroke end position
210 in the storage unit 80.
This takes place repeatedly as long as actual position values POS
at a position set-point value CMD of 100% are greater than the
stroke end position 210 stored in the storage unit 80.
The same applies to the specification of a position set-point value
CMD of 0%.
FIGS. 5a and 5c show simplified representations of the POS-time
curve. The associated simplified representations of the time curve
of the differentiating filter are shown in FIGS. 5b and 5d. FIG.
5a, 5b essentially correspond to FIG. 4a, 4b.
In the storage unit 80 of the valve control mechanism 20b,
travel-measurement system final values 100 and 110 for predefined
stroke end positions 200a, 210a are stored as default values.
The storage of the actual position values POS as stroke end values
200, 210 is always carried out when during the regular position
control operation (for example at time t8) a discontinuous
transition of the derivation function of the actual position value
POS to a stationary value occurs. The detection of the transition
is performed using a differentiating filter.
At times t5 or t7, the movement of the seal body begins in the
direction of 100% in accordance with the corresponding control
signal CTRL.
In FIG. 5a, at time t6, the physical stop of the actuator is
reached at the same time as the maximum actual position value
POSmax, i.e. the actual position value POS approaches the maximum
actual position value POSmax tangentially in the curve. The
associated characteristics in FIG. 5b show the corresponding
decrease in the slope of the POS curve.
In FIG. 5c, the physical stop of the actuator is reached at time
t8, i.e. the POS curve changes to a horizontal characteristic with
a kink. This kink is visible in the associated characteristic in
FIG. 5d, which depicts the derivation function of the actual
position value POS as a discontinuous transition to a stationary
value.
Although various embodiments have been disclosed, a worker of
ordinary skill in this art would recognize that certain
modifications would come within the scope of this disclosure. For
that reason, the following claims should be studied to determine
the true scope and content of this disclosure.
* * * * *